ask：

I have a buffer of RGB unsigned char that I would like converted into a bitmap file, does anyone know how?

My RGB float is of the following format

R [(0,0)], G[(0,0)], B[(0,0)],R [(0,1)], G[(0,1)], B[(0,1)], R [(0,2)], G[(0,2)], B[(0,2)] .....

The values for each data unit ranges from 0 to 255. anyone has any ideas how I can go about making this conversion?

 

 

answer：

You can use CGBitmapContextCreate to make a bitmap context from your raw data. Then you can create a CGImageRef from the bitmap context and save it. Unfortunately CGBitmapContextCreate is a little picky about the format of the data. It does not support 24-bit RGB data. The loop at the beginning swizzles the rgb data to rgba with an alpha value of zero at the end. You have to include and link with ApplicationServices framework.

 

char* rgba = (char*)malloc(width*height*4);
for(int i=0; i < width*height; ++i) {
    rgba[4*i] = myBuffer[3*i];
    rgba[4*i+1] = myBuffer[3*i+1];
    rgba[4*i+2] = myBuffer[3*i+2];
    rgba[4*i+3] = 0;
}
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef bitmapContext = CGBitmapContextCreate(
    rgba,
    width,
    height,
8, // bitsPerComponent
    4*width, // bytesPerRow
    colorSpace,
    kCGImageAlphaNoneSkipLast);

CFRelease(colorSpace);

CGImageRef cgImage = CGBitmapContextCreateImage(bitmapContext);
CFURLRef url = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, CFSTR("image.png"), kCFURLPOSIXPathStyle, false);

CFStringRef type = kUTTypePNG; // or kUTTypeBMP if you like
CGImageDestinationRef dest = CGImageDestinationCreateWithURL(url, type, 1, 0);

CGImageDestinationAddImage(dest, cgImage, 0);

CFRelease(cgImage);
CFRelease(bitmapContext);
CGImageDestinationFinalize(dest);
free(rgba);

 

 

int width = 11;
int height = 8;

Byte r[8][11]={
        {000,000,255,000,000,000,000,000,255,000,000},
        {000,000,000,255,000,000,000,255,000,000,000},  
        {000,000,255,255,255,255,255,255,255,000,000},
        {000,255,255,255,255,255,255,255,255,255,000},
        {255,255,255,255,255,255,255,255,255,255,255},
        {255,000,255,255,255,255,255,255,255,000,255},
        {255,000,255,000,000,000,000,000,255,000,255},
        {000,000,000,255,255,000,255,255,000,000,000}};

Byte g[8][11]={
        {000,000,255,000,000,000,000,000,255,000,000},
        {000,000,000,255,000,000,000,255,000,000,000},  
        {000,000,255,255,255,255,255,255,255,000,000},
        {000,255,255,000,255,255,255,000,255,255,000},
        {255,255,255,255,255,255,255,255,255,255,255},
        {255,000,255,255,255,255,255,255,255,000,255},
        {255,000,255,000,000,000,000,000,255,000,255},
        {000,000,000,255,255,000,255,255,000,000,000}};

Byte b[8][11]={
        {000,000,255,000,000,000,000,000,255,000,000},
        {000,000,000,255,000,000,000,255,000,000,000},  
        {000,000,255,255,255,255,255,255,255,000,000},
        {000,255,255,000,255,255,255,000,255,255,000},
        {255,255,255,255,255,255,255,255,255,255,255},
        {255,000,255,255,255,255,255,255,255,000,255},
        {255,000,255,000,000,000,000,000,255,000,255},
        {000,000,000,255,255,000,255,255,000,000,000}};

char* rgba = (char*)malloc(width*height*4);
int offset=0;
for(int i=0; i < height; ++i) 
{
for (int j=0; j < width; j++) 
        {
                rgba[4*offset]   = r[i][j];
                rgba[4*offset+1] = g[i][j];
                rgba[4*offset+2] = b[i][j];
                rgba[4*offset+3] = 0;
                offset ++;
        }
}


CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef bitmapContext = CGBitmapContextCreate(
    rgba,
    width,
    height,
8, // bitsPerComponent
    4*width, // bytesPerRow
    colorSpace,
    kCGImageAlphaNoneSkipLast                    
);

CFRelease(colorSpace);

CGImageRef cgImage = CGBitmapContextCreateImage(bitmapContext);

free(rgba);

UIImage *newUIImage = [UIImage imageWithCGImage:cgImage];

UIImageView *iv = [[UIImageView alloc] initWithFrame:CGRectMake(10, 10, 11,8)];

[iv setImage:newUIImage];

Then, addSubview:iv to get the image into your view and, of course, do the obligatory [releases]to keep a clean house.

 

 

 CGContextRef ctx = CGBitmapContextCreate(m_PixelBuf,  

                                                 CGImageGetWidth(grayImage),  

                                                 CGImageGetHeight(grayImage),  

                                                 CGImageGetBitsPerComponent(grayImage),

                                                 CGImageGetBytesPerRow(grayImage),  

                                                 CGImageGetColorSpace(grayImage), 

                                                 CGImageGetBitmapInfo(grayImage)

                                                 );

 

 

Creating Bitmap Contexts

Getting Information About Bitmap Contexts

These functions return the values of attributes specified when a bitmap context is created.

Functions

CGBitmapContextCreate

Creates a bitmap graphics context.

CGContextRef CGBitmapContextCreate (
 void *data,
 size_t width,
 size_t height,
 size_t bitsPerComponent,
 size_t bytesPerRow,
 CGColorSpaceRef colorspace,
 CGBitmapInfo bitmapInfo
);

 
 
    UIImage *dotline = [UIImage imageNamed:@"XXX.png"];
    UIGraphicsBeginImageContext(CGSizeMake(self.view.frame.size.width-4, 1));
    [dotline drawAsPatternInRect:CGRectMake(0, 0, self.view.frame.size.width-4, 1)];
return UIGraphicsGetImageFromCurrentImageContext();